Ceramic electronic device, paste coating method, and paste coating apparatus

ABSTRACT

A ceramic capacitor having a ceramic body and terminal electrodes, the ceramic body being substantially a rectangular parallelopiped in shape, the terminal electrodes being provided at the two ends of the ceramic body in the length direction, each terminal electrode being provided to cover one end face of the ceramic body in the length direction, part of the two surfaces in the width direction, and part of the two surfaces in the thickness direction, wherein, when the length of the ceramic body is L1 and the maximum lengths of the terminal electrodes at the two surfaces of the ceramic body in the width direction are L3 and L4, 0≦|(L4−L3|/L1≦0.0227 is satisfied. One surface among the two surfaces of the ceramic body in the width direction is the paste introduction side in the roller coating, while the other surface is the paste escape side in the roller coating.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a ceramic electronic device andto a paste coating method and paste coating apparatus used forproduction of that ceramic electronic device.

[0003] 2. Description of the Related Art

[0004] In chip capacitors and other ceramic electronic devices,cap-shaped terminal electrodes are formed at the two end faces of theceramic body. More particularly, each of these cap shaped terminalelectrodes is formed to cover one end face of the ceramic body in thelength direction, parts of the two surfaces of the body in the widthdirection, and parts of the two surfaces in the thickness direction.

[0005] To form such terminal electrodes, the general practice has beento use the method of dipping the ceramic body in a conductor paste orcoating by a roller to coat a conductive paste on the two ends of theceramic body and then dry the conductive paste by heat treatment tosolidify it.

[0006] Terminal electrodes formed by conductive paste sometimes differin the lengths of the parts formed on one surface in the width directionand the lengths of the parts formed on the other surface in the widthdirection due to the conditions under which the conductive paste iscoated.

[0007] If soldering on such a ceramic electronic device, the contactareas between the terminal electrode and solder at the two surfaces inthe width direction will end up differing. Therefore, the terminalelectrode will receive stress of different magnitudes from the solderand the inconvenience of the phenomenon of the ceramic body standing upon its own (Manhattan phenomenon) etc. will arise.

SUMMARY OF THE INVENTION

[0008] An object of the present invention is to provide a ceramicelectronic device able to avoid the Manhattan phenomenon of the ceramicbody in the soldering process and a paste coating method and pastecoating apparatus able to be used for production of such a ceramicelectronic device.

[0009] To achieve the above object, according to a first object of thepresent invention, there is provided a ceramic electronic device havinga ceramic body and terminal electrodes, wherein the ceramic body issubstantially a rectangular parallelopiped in shape; the electrodeterminals are provided at the two end sides of the ceramic body in thelength direction, each of the terminal electrodes provided to cover oneend face in the length direction of the ceramic body, part of the twosurfaces in the width direction, and part of the two surfaces in thethickness direction; and, when the length of the ceramic body is L1 andthe maximum lengths of the terminal electrodes at the two surfaces ofthe ceramic body in the width direction are L3 and L4,0≦|L4−L3|/L1≦0.0227 (1/44) is satisfied.

[0010] Experiments of the present inventors revealed that if the ratio(|L4−L3|/L1) is set in a range from 0 to 0.0227, the rate of occurrenceof the Manhattan phenomenon in the soldering process is kept low. Overthe ratio |L4−L3|/L1=0.0227, the rate of occurrence of the Manhattanphenomenon tends to abruptly increase. Therefore, according to theceramic electronic device of the present invention, it is possible toeffectively suppress the Manhattan phenomenon and eliminate thephenomenon of the ceramic body standing up in the soldering process.

[0011] Preferably, the ceramic body has a plurality of internalelectrodes, the plurality of internal electrodes being stacked insidethe ceramic body in the thickness direction at intervals from each otherand being connected to the terminal electrodes at one end surface eachin the length direction. The effect of the present invention isparticularly great in the case of a ceramic electronic device havingsuch a ceramic body.

[0012] Preferably, each of the terminal electrodes is formed by coatinga conductive paste on one end face of the ceramic body in the lengthdirection by roller coating and heat treating it.

[0013] In this case, preferably one surface among the two surfaces ofthe ceramic body in the width direction is a paste introduction side inthe roller coating, while the other surface is the paste escape side inthe roller coating.

[0014] Preferably, the boundary shapes of the terminal electrodes formedat parts of the two surfaces of the ceramic body in the width directionare different. More preferably, the boundary shapes of the terminalelectrodes formed at parts of the two surfaces of the ceramic body inthe width direction are different, with one being a projecting typeshape and the other being a recessed type shape. Alternatively, theboundary shapes of the terminal electrodes formed at parts of the twosurfaces of the ceramic body in the thickness direction are inclinedwith respect to the end faces of the ceramic body in the lengthdirection.

[0015] When forming a terminal electrode on one end face of the ceramicbody in the length direction by roller coating, the boundary shape withthe body of the terminal electrode easily becomes this shape. In thiscase, by applying the present invention, it is possible to effectivelysuppress the Manhattan phenomenon.

[0016] The surface of the terminal electrode may be formed with aplating film. This plating film may be a single layer or multiplelayers.

[0017] According to a second aspect of the present invention, there isprovided a paste coating method for forming terminal electrodescomprising the steps of rotating a roller coated with a conductive pasteon its outer circumference and moving a ceramic body in substantiallythe same direction as the direction of rotation of the roller andbringing one end surface of the ceramic body into contact with theconductive paste present on the outer circumference of the roller tocoat it with the conductive paste, wherein, when the speed of movementof the ceramic body is Vc and the peripheral speed of the roller at thecircumference in contact with the one end surface of the ceramic body isVp, the ratio Vp/Vc satisfies 0.95≦Vp/Vc≦0.98.

[0018] In this case, the ceramic body preferably has a plurality ofinternal electrodes, the plurality of internal electrodes being stackedinside the ceramic body at intervals from each other and being exposedat one end surface each of the ceramic body.

[0019] Experiments of the present inventors confirmed that by settingthe ratio Vp/Vc to a range of 0.95 to 0.98 and executing the pastecoating method, it is possible to keep the ratio (|L4−L3|/L1) of theterminal electrodes formed in the range from 0 to 0.0227. If setting theratio Vp/Vc larger than 0.98, the ratio (|L4−L3|/L1) of the terminalelectrodes exceeds 0.0227. Further, even if setting the ratio Vp/Vcsmaller than 0.95, the ratio (|L4−L3|/L1) of the terminal electrodesexceeds 0.0227.

[0020] By using the paste coating method of the present invention, it ispossible to effectively produce the above-mentioned ceramic electronicdevice resistant to the Manhattan phenomenon.

[0021] According to a third aspect of the present invention, there isprovided a paste coating apparatus including a paste coating roller forcoating a paste for forming terminal electrodes and a ceramic bodymovement device, the roller being driven to rotate; the ceramic bodymovement device moving the ceramic body in substantially the samedirection as the direction of rotation of the roller and bringing oneend surface of the ceramic body into contact with paste present on theouter circumference of the roller; and, when the speed of movement ofthe ceramic body is Vc and the peripheral speed of the roller at thecircumference in contact with the one surface of the ceramic body is Vp,the ratio Vp/Vc satisfies 0.95≦Vp/Vc≦0.98.

[0022] This paste coating apparatus is used to coat a conductive pasteon the outer circumference of the roller. It rotates the roller in thisstate and moves the ceramic body in substantially the same direction asthe rotational direction of the roller. Further, it brings one endsurface of the ceramic body into proximity with the outer circumferenceof the roller. Due to this, the conductive paste on the outercircumference of the roller is coated on that surface of the ceramicbody. Therefore, the above paste coating method is realized and theabove-mentioned ceramic electronic device according to the presentinvention is obtained.

[0023] Preferably, in the latter position of the direction of movementof the ceramic body with respect to the paste coating roller, ascrape-off roller is placed rotating in substantially the oppositedirection to the direction of movement of the ceramic body forcontrolling the thickness of the paste coated on the one surface of theceramic body.

[0024] By providing this scrape-off roller, it is possible to form aterminal electrode of a uniform predetermined thickness on one endsurface of the ceramic body.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] These and other objects and features of the present inventionwill become clearer from the following description of the preferredembodiments given with reference to the attached drawings, wherein:

[0026]FIG. 1 is a perspective view of a ceramic electronic deviceaccording to an embodiment of the present invention;

[0027]FIG. 2 is a cross-sectional view along the line II-II of FIG. 1;

[0028]FIG. 3 is a cross-sectional view of an electronic device withterminal electrodes without the plating film shown in FIG. 2;

[0029]FIG. 4 is a front view of an electronic device with terminalelectrodes without the plating film;

[0030]FIG. 5 is a back view of an electronic device with terminalelectrodes without the plating film;

[0031]FIG. 6 is a plan view of an electronic device with terminalelectrodes without the plating film;

[0032]FIG. 7 is a graph of the number of occurrences of the Manhattanphenomenon with respect to the ratio (|L4−L3|/L1);

[0033]FIG. 8 is a schematic view of the configuration of a paste coatingapparatus;

[0034]FIG. 9 is a partial enlarged cross-sectional view of the pastecoating apparatus shown in FIG. 8;

[0035]FIG. 10 is graph of lengths L3 and L4 of terminal electrodes withrespect to the ratio Vp/Vc;

[0036]FIG. 11 is a graph of the characteristic of the ratio (|L4−L3|/L1)with respect to the ratio Vp/Vc;

[0037]FIG. 12 is graph of lengths L5 and L6 of terminal electrodes withrespect to the ratio Vp/Vc; and

[0038]FIG. 13 is a graph of the characteristic of the ratio (|L6−L5|/L1)with respect to the ratio Vp/Vc.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] Preferred embodiments of the present invention will be describedin detail below while referring to the attached figures.

[0040] Ceramic Electronic Device

[0041] As shown in FIG. 1 and FIG. 2, the ceramic electronic deviceaccording to an embodiment of the present invention has a ceramic body 1and terminal electrodes 31 and 32. The “ceramic electronic device”includes a chip capacitor, chip inductor, chip varistor, or chipresistor or combinations of the same. Note that in the figures, a chipcapacitor is shown as one example of a ceramic electronic device.

[0042] The ceramic body 1 is substantially a rectangular parallelepipedin shape. Note that the expression “rectangular parallelepiped” includesrectangular parallelepiped with rounded corners and rectangularparallelepiped which are chamfered. The length L1 along the lengthdirection L of the ceramic body 1, the width W1 along the widthdirection W, and the thickness T1 along the thickness direction T may beany values. In the case of the illustrated embodiment, the values are asfollows: length L1=2.0 mm, width W1=1.2 mm, and thickness T1=1.25 mm. Asanother example, they may be a length L1=4.4 mm, a width W1=3.1 mm, anda thickness T1=2.2 mm.

[0043] The relative magnitude of the length L1, width W1, and thicknessT1 is length L1>width W1 and length L1>thickness T1. The ceramic body 1may be formed from a known ceramic material selected in accordance withthe type of the ceramic electronic device. Note that the lengthdirection L is the direction in which the terminal electrodes are formedat the two ends of the ceramic body 1, while the thickness direction Tis the direction in which the internal electrodes 21 to 28 shown in FIG.2 and the dielectric layers formed between them are stacked. Further,the width direction W is the direction substantially perpendicular toboth the length direction L and thickness direction T.

[0044] Referring to FIG. 2, the ceramic body 1 has a plurality ofinternal electrodes 21 to 28. The plurality of internal electrodes 21 to28 are stacked inside the body in the thickness direction T viadielectric layers. In the present embodiment, the alternate internalelectrodes 21, 23, 25, and 27 stacked via dielectric layers areconnected to only one terminal electrode 31, while the other internalelectrodes 22, 24, 26, and 28 are connected to only the other terminalelectrode 32, so as to form a multilayer capacitor circuit. Note thatthe number of the internal electrodes 21 to 28 is not particularlylimited in the present invention.

[0045] Referring to FIG. 3, the terminal electrodes 31 and 32 areprovided at the two sides of the ceramic body 1 in the length directionL. Further referring to FIG. 4 to FIG. 6 as well, one terminal electrode31 is provided so as to cover one end surface 11 of the body 1 in thelength direction L, parts of the two surfaces 13 and 14 in the widthdirection W, and parts of the two surfaces 15 and 16 in the thicknessdirection T. The other terminal electrode 32 is provided so as to coverthe other end surface 12 in the length direction L, parts of the twosurfaces 13 and 14 in the width direction W, and parts of the twosurfaces 15 and 16 in the thickness direction T.

[0046] Referring to FIG. 4, one terminal electrode 31 covers the part ofthe surface 13 in the width direction W near one end surface 11 in thelength direction L. The other terminal electrode 32 covers the part ofthe surface 13 in the width direction W near the other end surface 12 inthe length direction L. Note that the terminal electrodes 31 and 32 aredifficult to form at uniform widths (length direction L of body 1) atthe two ends of the ceramic body 1 in the length direction L. Theysometimes become recessed as the center as shown in FIG. 4, project outat the center as shown in FIG. 5, or become asymmetric at the two sidesas shown in FIG. 6. The paste coating method by the paste coatingapparatus explained later has a large influence over such shapes.

[0047] In FIG. 4, the maximum length of the terminal electrodes 31 and32 at the surface 13 in the width direction W is made L3. In FIG. 4,however, the boundary shapes of the terminal electrodes 31 and 32 arerecessed shapes with recessed centers. The two side parts generally havemaximum lengths of L3, but the parts of the maximum length L3 are notalways there. The maximum lengths L3 of the terminal electrodes 31 and32 should be the same when forming them under the same conditions by thelater explained paste coating apparatus.

[0048] Referring to FIG. 5, one terminal electrode 31 covers the part ofthe other surface 14 in the width direction near one end surface 11 inthe length direction L. The other terminal electrode 32 covers the partof the other surface 14 in the width direction W near the other endsurface 12 in the length direction. The maximum length of the terminalelectrodes 31 and 32 at the other surface 14 in the width direction W ismade L4. Note that in FIG. 5, the terminal electrodes 31 and 32 haveprojecting boundary shapes with projecting centers. The center partsgenerally have the maximum lengths of L4, but the parts of the maximumlength L4 are not always the centers. The maximum lengths L4 of theterminal electrodes 31 and 32 should be the same when forming them underthe same conditions by the later explained paste coating apparatus.

[0049] Referring to FIG. 6, one terminal electrode 31 covers the part ofthe surface 15 in the thickness direction T near the end surface 11 inthe length direction L. The other terminal electrode 32 covers the partof the surface 15 in the thickness direction T near the other endsurface 12 in the length direction L. When viewed from the thicknessdirection T surface 15 side, the boundary shapes of the terminalelectrodes 31 and 32 with the body are inclined with respect to the endfaces 11 and 12. Further, the lengths of the terminal electrodes 31 and32 on the surface 13 in the width direction W are made L5, while thelengths of the terminal electrodes 31 and 32 on the other surface 14 inthe width direction W are made L6. In the present embodiment, the lengthL5 positioned at the surface 13 in the width direction W serving as thepaste introduction side in the later explained roller coating is smallerthan the length L6 positioned at the surface 14 in the width direction Wserving as the paste escape side.

[0050] This length L5 often matches with the maximum length L3 shown inFIG. 4, but the length L6 is often shorter than the maximum length L4shown in FIG. 5. Note that at the other surface 16 in the thicknessdirection T as well, the boundary shapes of the terminal electrodes 31and 32 are similar to the boundary shapes of the terminal electrodes 31and 32 at the surface 15.

[0051] Referring to FIG. 3, one terminal electrode 31 is connected tothe internal electrodes 21, 23, 25, and 27 at one surface 11 of theceramic body 1 in the length direction L. The other terminal electrode32 is connected to the internal electrodes 22, 24, 26, and 28 at theother surface 12 of the ceramic body 1 in the length direction L.

[0052] The terminal electrodes 31 and 32 are electrodes baked on theceramic body 1. These terminal electrodes 31 and 32 are obtained bycoating a conductive paste on the ceramic body 1 and drying andsolidifying the conductive paste by heat treatment.

[0053] Referring again to FIG. 1 and FIG. 2, the surfaces of theterminal electrodes 31 and 32 have plating films 41 and 42 deposited onthem. Further, the surfaces of these plating films 41 and 42 haveplating films 43 and 44 deposited on them. These plating films 41 to 44are metal films of Cu, Ni, Sn, etc.

[0054] The lengths L3 and L4 of the terminal electrode 31 (see FIG. 4and FIG. 5) are far larger than the thicknesses of the plating films 41and 43 deposited on the surface of the terminal electrode 31. Thethicknesses of the plating films 41 and 43 are substantially negligible.Similarly, the lengths L3 and L4 of the terminal electrode 32 are farlarger than the thicknesses of the plating films 42 and 44 deposited onthe surface of the terminal electrode 32 and the thicknesses of theplating films 42 and 44 are substantially negligible.

[0055] The important characteristic of the ceramic electronic deviceaccording to the present invention is that the length L1 of the ceramicbody 1, the length L3 of the terminal electrodes 31 and 32 at the widthdirection W surface 13 side and the length L4 of the terminal electrodes31 and 32 at the other width direction W surface 14 side satisfy

0≦|L4−L3|/L1≦0.0227(1/44)  (1)

[0056] For example, if the length L1 of the ceramic body 1 is 2.0 mm,the above relation (1) becomes 0≦|L4−L3|≦0.046(1/22) mm

[0057] <Experimental Data>

[0058] Next, experimental data will be explained. Five sample groups 1to 5 of ceramic electronic devices of the above configuration changedprogressively in the ratio (|L4−L3|/L1) of the terminal electrodes 31and 32 were prepared. The sample groups 1 to 5 each included 100samples. The ratios (|L4−L3|/L1) of the sample groups 1 to 5 were made0.002(1/500), 0.011(1/91), 0.021(1/48), 0.031(1/32), and 0.041(1/24).These values, however, were mean values of the 100 samples included inthe respective sample groups.

[0059] Next, soldering processes were applied to these sample groups 1to 5 to investigate the occurrence of the Manhattan phenomenon. In thesoldering processes, eutectic solder was used and the reflow temperaturewas made 240° C. The results are shown in the following Table 1. TABLE 1No. of occurrences Ratio (|L4-L3|/L1) of Manhattan Sample group no.(mean value) phenomenon 1 0.002 0 2 0.011 1 3 0.021 0 4 0.031 5 5 0.0414

[0060] Next, the number of occurrences of the Manhattan phenomenon withrespect to the ratio (|L4−L3|/L1) was graphed and approximated. Thecurve is shown by reference U8 in FIG. 7. Referring to this curve U8, inthe range of the ratio (|L4−L3|/L1) from 0 to 0.0227, the number ofoccurrences of the Manhattan phenomenon in the soldering process is keptlow. Over a ratio |L4−L3|/L1=0.0227, the number of occurrences of theManhattan phenomenon abruptly increases.

[0061] Above, the case of application of the present invention to a chipcapacitor as one type of ceramic electronic device was explained, butthe present invention can also be applied to other types of ceramicelectronic devices.

[0062] Paste Coating Method and Paste Coating Apparatus

[0063] Next, the paste coating method and paste coating apparatus usedfor production of the above ceramic electronic device will be explained.

[0064] As shown in FIG. 8, the paste coating apparatus according to oneembodiment of the present invention includes a paste coating roller 61and a ceramic body movement device 8.

[0065] The roller 61 is driven to rotate in the direction indicated bythe arrow a1 by a drive device 71. The outer circumference of the roller61 is coated with a conductive paste 35. Specifically, the bottom of theroller 61 is immersed in the conductive paste 35 placed in a container37. By driving the roller 61 to rotate, the outer circumference of theroller 61 is coated with the conductive paste 35. The conductive paste35 is formed from a material having a known composition, viscosity, andelectrical characteristics.

[0066] The roller 61 has a stationary squeegee 67 provided near it. Thestationary squeegee 67 scrapes off the excess conductive paste 35 coatedon the outer circumference of the roller 61 to ensure a uniformthickness of the conductive paste 35 coated on the outer circumferenceof the roller 61.

[0067] As shown in FIG. 8 and FIG. 9, the ceramic body movementapparatus 8 moves the ceramic body 1 in the tangential direction a3 ofthe rotational direction a1 of the roller 61 to bring one surface 11 ofthe ceramic body 1 in the length direction L into proximity with theouter circumference of the roller 61. The ceramic body 1 is the same asthe ceramic body 1 explained with reference to FIG. 1 and FIG. 2 and isin the state before formation of the terminal electrodes 31 and 32.

[0068] The movement direction a3 of the ceramic body 1 becomessubstantially perpendicular to the shaft 611 of the roller 61. Theceramic body movement device 8 specifically has a belt 83 and guideroller 85 and 86.

[0069] The belt 83 is provided with a plurality of fasteners 81. Thesefasteners 81 are provided at intervals on the belt 83. ceramic bodies 1are affixed to the belt 83 through these fasteners 81.

[0070] The belt 83 is stretched between the guide rollers 85 and 86. Theguide roller 86 is driven to rotate in the direction indicated by thearrow a4 by a drive device 73. Due to this, the belt 83 travels in thedirection of the arrow a3. The ceramic bodies 1 fastened to the belt 83also are moved in the direction of the arrow a3.

[0071] Referring to FIG. 8, the paste coating apparatus is provided witha scraper roller 62. This scraper roller 62 is provided after the roller61 in the direction of the arrow a3 and is driven to rotate in thedirection a2 opposite to the movement direction a3 of the ceramic body 1by a drive device 72. That is, the rotational direction a2 is reverse tothe rotational direction a3. The scraper roller 62 is provided with astationary squeegee 68. The stationary squeegee 68 serves to remove dirtfrom the outer circumference of the scrape-off roller 62.

[0072] The ceramic body movement device 8 brings the surface 11 of theceramic body 1 into proximity with the roller 61 as explained above,then moves the ceramic body 1 in the direction a3 opposite to therotational direction a2 of the scraper roller 62 and moves the surface11 of the ceramic body 1 into proximity with the outer circumference ofthe scraper roller 62.

[0073] The paste coating apparatus is provided with a control device 75.The control device 75 gives a control signal S1 to the drive device 71to control the rotation of the roller 61 through the drive device 71.Similarly, the control device 75 gives a control signal S2 to the drivedevice to control the rotation of the roller 62 through the drive device72. Further, the control device 75 gives a control signal S3 to thedrive device 73 to control the travel of the belt 83 through the drivedevice 73 and the guide roller 86.

[0074] Referring to FIG. 8 and FIG. 9, the apparatus rotates the roller61 coated on its outer circumference with a conductive paste 35, movesthe ceramic body 1 in the tangential direction a3 of the same directionas the rotational direction a1 of the roller 61, and brings the surface11 of the ceramic body 1 in the length direction L into proximity withthe outer circumference of the roller 61. Due to this, the conductivepaste 35 on the outer circumference of the roller 61 is coated on andnear the surface 11 of the ceramic body 1 in the length direction L. Theone surface 13 among the two surfaces 13 and 14 of the ceramic body 1 inthe width direction W becomes the paste introduction side, while theother surface 14 becomes the paste escape side (see FIG. 9).

[0075] As shown in FIG. 9, when the speed of movement of the ceramicbody 1 is made Vc and the peripheral speed of the roller 61 as seen atthe circumference Crl in contact with the surface 11 of the ceramicroller 1 is made Vp, to obtain the ceramic electronic device shown inFIG. 1 to FIG. 6, it is sufficient to set the ratio Vp/Vc of the roller61 and ceramic body movement device 8 to satisfy:

0.95 ≦Vp/Vc≦0.98  (2)

[0076] In the illustrated embodiment, the ratio Vp/Vc can be controlledby the control device 75.

[0077] Note that the circumference Crl shown in FIG. 9 is at a positionof a distance L7 from the outer circumference of the roller 61 ofpreferably 0 to 0.8 mm. Further, the thickness L8 of the conductivepaste 35 formed on the outer circumference of the roller 61 is athickness of 3 to 12 times the distance L7.

[0078] Next, as explained with reference to FIG. 8, the apparatusrotates the scraper roller 62 in the direction indicated by the arrowa2, moves the ceramic body 1 in a direction a3 opposite to therotational direction a2 of the scraper roller 62, and brings the surface11 of the ceramic body 1 into proximity with the outer circumference ofthe scraper roller 62. Therefore, the excess portion of the conductivepaste 35 formed on the surface 11 of the ceramic body 1 is scraped offfrom the outer circumference of the scraper roller 62.

[0079] Next, the conductive paste 35 coated on the surface 11 of theceramic body 1 is dried and solidified by heat treatment. By applying asimilar paste coating process and heat treatment to the opposite surface12 of the ceramic body 1, the terminal electrodes 31 and 32 shown inFIG. 1 to FIG. 6 are obtained.

[0080] <Experimental Data>

[0081] Next, experimental data will be explained. In the above pastecoating method, the speed of movement Vc of the ceramic body 1 was fixedand the peripheral speed Vp of the roller 61 as seen at thecircumference Crl contacting the surface 11 of the ceramic body 1 wasprogressively changed (see following Table 2). Due to this, the ratioVp/Vc was progressively changed. The result are shown as Numerical ValueExamples 1 to 6. TABLE 2 Speed of Peripheral Peripheral movement speedof speed Vp of Numerical Vc of outer roller 61 value ceramiccircumference seen at example body 1 of roller 61 circumference Rationo. (mm/s) (mm/s) Cr1 (mm/s) Vp/Vc 1 6.000 5.700 5.719 0.953 2 6.0005.800 5.819 0.970 3 6.000 5.900 5.920 0.987 4 6.000 6.000 6.020 1.003 56.000 6.100 6.120 1.020 6 6.000 6.200 6.221 1.037

[0082] The peripheral speed Vp of the roller 61 as seen at thecircumference Cr1 in contact with the surface 11 of the ceramic body 1is found from the peripheral speed of the outer circumference of theroller 61. The distance L7 between the outer circumference of the roller61 and the surface 11 of the ceramic body (see FIG. 9) was made 0.1 mm.Further, the thickness L8 of the conductive paste 35 coated on the outercircumference of the roller 61 was made 1.1 mm.

[0083] Using the paste coating method of each of Numerical ValueExamples 1 to 6, conductive paste 35 was coated on and near the surface11 of the ceramic body 1 in the length direction L. The length L1, widthW1, and thickness T1 of the ceramic body 1 were made 2.0 mm, 1.2 mm, and1.25 mm, respectively. Further, the composition and the viscosity of theconductive paste 35 were as follows:

[0084] <Paste Composition>

[0085] Metal ingredient: Ag 100%

[0086] Metal content: 73 wt %

[0087] Binder: acrylic-based resin

[0088] <Paste Viscosity>

[0089] 1 rpm: 80 Pa·s

[0090] 10 rpm: 35 Pa·s

[0091] 100 rpm: 23 Pa·s

[0092] Here, the paste viscosity is the value measured by a BF viscositymeter.

[0093] Next, the coated conductive paste 35 was dried and solidified byheat treatment. Due to this, a sample provided with a terminal electrode31 on the surface 11 of the ceramic body 1 was obtained. Five types ofsamples were obtained for each of the Numerical Value Examples 1 to 6.

[0094] Next, the length L3 of the terminal electrode 31 at the widthdirection W surface 13 side and the length L4 of the terminal electrode31 at the width direction W surface 14 side were measured (see FIG. 4and FIG. 5). Further, the length L5 of the terminal electrode 31 on thesurface 13 in the width direction W and the length L6 of the terminalelectrode 31 on the other surface 14 in the width direction W when seenfrom the thickness direction T surface 15 side were measured. Thesurface 13 is the paste introduction surface, while the surface 14 isthe paste escape surface (see FIG. 9). The lengths L3 to L6 weremeasured by a projector.

[0095]FIG. 10 is a graph of the lengths L3 and L4 of the terminalelectrode 31 with respect to the ratio Vp/Vc. In the figure, thecharacteristic of the length L3 with respect to the ratio Vp/Vc and thecharacteristic of the length L4 with respect to the ratio Vp/Vc areshown by references U3 and U4, respectively. Referring to thecharacteristics U3 and U4, the larger the ratio Vp/Vc, the shorter thelength L3 of the terminal electrode 31 on the paste introduction sidesurface 13 and the longer the length L4 of the terminal electrode 31 onthe paste escape side surface 14.

[0096]FIG. 11 is a graph of the characteristic U1 of the ratio(|L4−L3|/L1) with respect to the ratio Vp/Vc. This characteristic U1 isfound from the characteristics U3 and U4 shown in FIG. 10. In the rangeof the Vp/Vc of 0.96 or less, the smaller the ratio Vp/Vc, the greaterthe ratio (|L4−L3|/L1). When the ratio Vp/Vc becomes smaller than 0.95,the ratio (|L4−L3|/L1) exceeds 0.0227. Therefore, the lower limit of theratio Vp/Vc was made 0.95.

[0097] Further, in the range of the Vp/Vc of 0.97 or more, the largerthe ratio Vp/Vc, the greater the ratio (|L4−L3|/L1) When the ratio Vp/Vcbecomes greater than 0.98, the ratio (|L4−L3|/L1) exceeds 0.0227.Therefore, the upper limit of the ratio Vp/Vc was made 0.98.

[0098] If the ratio Vp/Vc is set in a range B1 of 0.95<Vp/Vp<0.98 inthis way, it is possible to keep the ratio (|L4−L3|/L1) of the terminalelectrode 31 within the range of 0<(|L4−L3|/L1)<0.0227.

[0099]FIG. 12 is a graph of the lengths L5 and L6 of the terminalelectrode 31 with respect to the ratio Vp/Vc. In the figure, thecharacteristic of the length L5 with respect to the ratio Vp/Vc and thecharacteristic of the length L6 with respect to the ratio Vp/Vc areshown by references U5 and U6, respectively.

[0100] Referring to the characteristics U5 and U6 shown in FIG. 12, thelarger the ratio Vp/Vc, the shorter the length L5 of the terminalelectrode 31 on the paste introduction side surface 13 when seen fromthe thickness direction T surface 15 side and the longer the length L6of the terminal electrode 31 on the paste escape side surface 14.

[0101]FIG. 13 is a graph of the characteristic U2 of the ratio(|L6−L5|/L1) with respect to the ratio Vp/Vc. This characteristic U2 isfound from the characteristics U5 and U6 shown in FIG. 12. If the ratioVp/Vc is set in a range B1 of 0.95≦Vp/Vp≦0.98, it is possible to keepthe ratio (|L6−L5|/L1) of the terminal electrode 31 within the range B3of 0≦(|L6−L5|/L1)<0.0227.

[0102] As explained above, according to the present invention, it ispossible to provide a ceramic electronic device able to avoid theManhattan phenomenon of the ceramic body in the soldering process and apaste coating method and paste coating apparatus able to be used forproduction of such a ceramic electronic device.

[0103] While the invention has been described with reference to specificembodiments chosen for purpose of illustration, it should be apparentthat numerous modifications could be made thereto by those skilled inthe art without departing from the basic concept and scope of theinvention.

What is claimed is:
 1. A paste coating method for forming terminalelectrodes comprising the steps of: rotating a roller coated with aconductive paste on its outer circumference and moving a ceramic body insubstantially the same direction as the direction of rotation of saidroller and bringing one end surface of said ceramic body into contactwith said conductive paste present on the outer circumference of saidroller to coat the end surface with said conductive paste, wherein, whenthe speed of movement of said ceramic body is Vc and the peripheralspeed of said roller at the circumference in contact with said onesurface of said ceramic body is Vp, the ratio Vp/Vc satisfies0.95≦Vp/Vc≦0.98.
 2. The paste coating method as set forth in claim 1,wherein said ceramic body has a plurality of internal electrodes, saidplurality of internal electrodes being stacked inside said ceramic bodyat intervals from each other and being exposed at said one surface eachof said ceramic body.
 3. A paste coating apparatus including a pastecoating roller for coating a paste for forming a terminal electrode anda ceramic body movement device, said roller being driven to rotate; saidceramic body movement device moving said ceramic body in substantiallythe same direction as the direction of rotation of said roller andbringing one end surface of said ceramic body into contact with pastepresent on the outer circumference of said roller; and, when the speedof movement of said ceramic body is Vc and the peripheral speed of saidroller at the circumference in contact with said one surface of saidceramic body is Vp, the ratio Vp/Vc satisfies 0.95≦Vp/Vc≦0.98.
 4. Thepaste coating apparatus as set forth in claim 3, wherein, in the latterposition of the direction of movement of said ceramic body with respectto said paste coating roller, a scraper roller is placed rotating insubstantially the opposite direction to the direction of movement ofsaid ceramic body for controlling the thickness of the paste coated onsaid one surface of said ceramic body.